DESCRIPTION (Applicant's Description): The proposed research concerns the morphological organization of the inner retina of the mouse. This is important because of the paucity of information about the mouse retina, at a time when the mouse is gaining increasing relevance as an animal model thanks to the advent of genetic manipulations. We propose to continue a study concerning the identification and quantitative distribution of the major populations of cells in the inner retina of the mouse. We will build an anatomical database that can be used as a base of reference for scientists studying the development and the adult retinal organization in normal and genetically-altered mammals. The outcome of building a database for the retina of the mouse will be immediate: we propose to assess the morphological integrity of inner retinal neurons in mice with inherited photoreceptor degeneration. Possible strategies for treating similar degeneration in humans include photoreceptor transplantation and electronic (prosthetic) stimulation of the retina. They are based upon the assumption that the inner retina is not at all affected by photoreceptor loss, but there is very little experimental evidence that this is indeed true. On the contrary, the existing literature points to a specific loss of inner retinal neurons, which would impair any attempt to restore vision through photoreceptor replacement. Any outcome of this research is useful: if no changes are observed consequent to photoreceptor degeneration in either morphology or overall distribution of single types of inner retinal cells, then it can be concluded that inner retinal changes secondary to photoreceptor are of limited relevance. If selective alterations are identified, they have to be taken into account when devising new therapeutic strategies. They would also become candidates as contributors to the secondary degeneration of cones that follows loss of rods.